JdbcTemplate错误总结

末蓝、 2022-04-24 04:10 412阅读 0赞

## 一、Spring对jdbc操作的简化 ##

> 1、连接管理  
> 2、jdbc操作重复代码封装

## 二、JdbcTemplate的问题 ##

在简化jdbc操作过程中，JdbcTemplate是不可或缺的重要一环。具体问题咱们在代码中解释理解吧。  
下面是通过**xml配置文件**依赖注入：JdbcTemplate对象

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:p="http://www.springframework.org/schema/p"
        xmlns:context="http://www.springframework.org/schema/context"
        xmlns:aop="http://www.springframework.org/schema/aop"
        xsi:schemaLocation="
            http://www.springframework.org/schema/beans
            http://www.springframework.org/schema/beans/spring-beans.xsd
            http://www.springframework.org/schema/context
            http://www.springframework.org/schema/context/spring-context.xsd
            http://www.springframework.org/schema/aop
            http://www.springframework.org/schema/aop/spring-aop.xsd">
        
        
        
        <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
           <property name="driverClass" value="com.mysql.jdbc.Driver"></property>
           <property name="jdbcUrl" value="jdbc:mysql://localhost:3306/study_of_mypool"></property>
           <property name="user" value="root"></property>
           <property name="password" value="root"></property>
           <property name="initialPoolSize" value="3"></property>
    	   <property name="maxPoolSize" value="10"></property>
    	   <property name="maxStatements" value="100"></property>
    	   <property name="acquireIncrement" value="2"></property>
        </bean>
        
        <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
           <property name="dataSource" ref="dataSource"></property>
        </bean> 
        
        
         
        
    </beans>

**UserDao实体类部分：**

public class UserDao {
    	/**
    	 * spring 可以做到对jdbc操作的简化：
    	 *  1、连接管理 
    	 * 2、jdbc操作重复代码封装
    	 */
    	// 注入IOC容器
    	public JdbcTemplate jdbcTemplate;
    	public void setjdbcTemplate(JdbcTemplate jdbcTemplate) {
    	
    		this.jdbcTemplate = jdbcTemplate;
    	}
    	//使用JdbcTemplate组件
    	public void save() {
    		
    			String sql = "INSERT INTO detp(deptName) VALUES('test');";
    			
    			jdbcTemplate.update(sql);
    			
    			
    	}
    	/**
    	 * 2、jdbc操作重复代码封装
    	 */
    	public Detp findById(int id) {
    		String sql = "select * from detp where deptId=?";
    		List<Detp> list = jdbcTemplate.query(sql, new MyResult(),id);
    		return (list!=null&&list.size()>0) ? list.get(0) : null;
    	}
    	
    	class MyResult implements RowMapper<Detp>{
           
    		//如何封装一条记录
    		@Override
    		public Detp mapRow(ResultSet arg0, int arg1) throws SQLException {
    			Detp detp = new Detp();
    			detp.setDeptId(arg0.getInt("deptId"));
    			detp.setDeptName(arg0.getString("deptName"));
    			return detp;
    		}
    	}
    }

**主程序调用：**

public class App {
    	
    	//获取IOC容器对象
    	ApplicationContext ac = new ClassPathXmlApplicationContext("step10_jdbc/application.xml");
    	
    	@Test
    	public void testjdbc()
    	{
    //		UserDao userDao =  (UserDao) ac.getBean("userDao");
    
    		JdbcTemplate jdbcTemplate = (JdbcTemplate) ac.getBean("jdbcTemplate");
    		UserDao userDao = new UserDao();
    		userDao.setjdbcTemplate(jdbcTemplate);
    		userDao.save();
    		
    //		System.out.println(userDao.findById(2));
    	}
    }

当采用userDao依赖注入，在主程序通过\*\*ac.getBean(“jdbcTemplate”);\*\*调用时会出现以下错误：

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userDao' defined in class path resource [step10_jdbc/application.xml]: Initialization of bean failed; nested exception is org.springframework.beans.ConversionNotSupportedException: Failed to convert property value of type 'java.lang.String' to required type 'org.springframework.jdbc.core.JdbcTemplate' for property 'jdbcTemplate'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'java.lang.String' to required type 'org.springframework.jdbc.core.JdbcTemplate' for property 'jdbcTemplate': no matching editors or conversion strategy found
    	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:584)
    	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:498)
    	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320)
    	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318)
    	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199)
    	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:846)
    	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:863)
    	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:546)
    	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:144)
    	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:85)
    	at step10_jdbc.App.<init>(App.java:11)
    	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    	at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    	at java.lang.reflect.Constructor.newInstance(Unknown Source)
    	at org.junit.runners.BlockJUnit4ClassRunner.createTest(BlockJUnit4ClassRunner.java:217)
    	at org.junit.runners.BlockJUnit4ClassRunner$1.runReflectiveCall(BlockJUnit4ClassRunner.java:266)
    	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    	at org.junit.runners.BlockJUnit4ClassRunner.methodBlock(BlockJUnit4ClassRunner.java:263)
    	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
    	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    	at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:89)
    	at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:41)
    	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:541)
    	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:763)
    	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:463)
    	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:209)
    Caused by: org.springframework.beans.ConversionNotSupportedException: Failed to convert property value of type 'java.lang.String' to required type 'org.springframework.jdbc.core.JdbcTemplate' for property 'jdbcTemplate'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'java.lang.String' to required type 'org.springframework.jdbc.core.JdbcTemplate' for property 'jdbcTemplate': no matching editors or conversion strategy found
    	at org.springframework.beans.AbstractNestablePropertyAccessor.convertIfNecessary(AbstractNestablePropertyAccessor.java:590)
    	at org.springframework.beans.AbstractNestablePropertyAccessor.convertForProperty(AbstractNestablePropertyAccessor.java:604)
    	at org.springframework.beans.BeanWrapperImpl.convertForProperty(BeanWrapperImpl.java:219)
    	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.convertForProperty(AbstractAutowireCapableBeanFactory.java:1697)
    	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1653)
    	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1400)
    	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:575)
    	... 33 more
    Caused by: java.lang.IllegalStateException: Cannot convert value of type 'java.lang.String' to required type 'org.springframework.jdbc.core.JdbcTemplate' for property 'jdbcTemplate': no matching editors or conversion strategy found
    	at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:299)
    	at org.springframework.beans.AbstractNestablePropertyAccessor.convertIfNecessary(AbstractNestablePropertyAccessor.java:585)
    	... 39 more

在一直未能解决的情况下，我将UserDao对象未注入IOC容器，而是直接创建对象，通过\*\*ac.getBean(“jdbcTemplate”)\*\*来获取JdbcTemplate，并将其传入UserDao对象，然后调用save方法，这样可以顺利通过。

> 花费几个小时时间也不能理解为什么不能注入UserDao对象，希望明天可以得到解决，在此做一下记录，如果有相同错误已得到解决的朋友可以指点一下，谢谢啦！